Snap, Crackle, POP!

[texaninsouthfl]

I know there's been quite a bit of discussion over time on the subject of popping and backfiring upon decel and I've read through most, if not all of it but thought I'd relate the particular symptoms in my case and get suggestions of where to start looking first...

Let me say first that after reading all the other posts, I did the one thing I felt pretty sure my somewhat limited wrenching ability could handle...  I tightened both the carb boot screws and header nuts. I've actually done that twice... first when I got the bike and started reading the forum and recently.

I acquired my Valk about 4 months ago... she has the 6 into 6 pipes with no baffles but I'm not sure of the make, she has not been de-smogged, I don't know if she was re-jetted. She ran great and there was more of a burble than a pop upon decel. I've run a few tanks with Sea Foam and I ride nearly every day and have put about 5500 miles on her.

A week or ten days ago, I noticed an occasional sharp pop from one cylinder on the left bank ... it didn't happen all the time and it was sometimes on decel and now and again on a low to medium throttle up shift. (just one pop on upshift) The problem gradually worsened on the left bank and then started the right bank at moderate speed decel... and now upon decel at all speeds... from mild pops to real nasty backfiring... it's constant enough to annoy the living hell out of me. I went on a charity ride today and the guy riding behind me laughingly mentioned that my bike had some "interesting sound effects." 

The only variable was that I changed the spark plugs a while back... standard plugs as called for... and it was at least a couple of weeks after that that the cursed popping started so I doubt it has anything to do with the plugs... I only mention it because it is the only thing on the bike that has changed (except engine and final drive oil) since I got the bike.

Soooo.... given my modest wrenching abilities (I don't have much experience but I'm fairly good at following  "destructions") where do y'all suggest I start looking first?

Oh, by the way, there are no other running issues... starts, idles, accelerates and cruises just like it always has... no change in mileage... just the *&#@%^* infernal popping..

[Smokinjoe-VRCCDS#0005]

If the 6X6 are slash cut they are Cobra's....If they have a turn at the end they are Two-Brothers....If you put some baffles in , it will stop most if not all the popping ( I've been there with my bikes that all have Cobra's ).I'm betting if it has no baffles you have Cobra see picture below ...I'm not sure you can remove the Two-Brothers because of the turn-out  

[texaninsouthfl]

If the 6X6 are slash cut they are Cobra's....If they have a turn at the end they are Two-Brothers....If you put some baffles in , it will stop most if not all the popping ( I've been there with my bikes that all have Cobra's ).I'm betting if it has no baffles you have Cobra ...I'm not sure you can remove the Two-Brothers because of the turn-out 

Thanks for the idea... but the pipes had the baffles out when I bought the bike and there was very little if any popping 5000 miles ago ... now there is, so something must have changed.

[GreenLantern57]

Did you use Japanese plugs?  I used a name brand once on my Magna and they fouled quickly. Went back to NKG, Nippon (?) and she ran like a top to the day she died.

[PhredValk]

Was it a local bike when you bought it? If not you could be experiencing elevation or fuel change issues.
If so, you may have to rejet or play with the pilot screws.
Fred.

[Skinhead]

Check the O-rings and all vacuum hoses & caps, or better yet, desmog!

[texaninsouthfl]

Did you use Japanese plugs?  I used a name brand once on my Magna and they fouled quickly. Went back to NKG, Nippon (?) and she ran like a top to the day she died.

I used NGK plugs.

[texaninsouthfl]

Was it a local bike when you bought it? If not you could be experiencing elevation or fuel change issues.
If so, you may have to rejet or play with the pilot screws.
Fred.

Local.

[9Ball]

probably vacuum hoses, vacuum caps, and or intake o-rings...recommend redeyetech on ebay.

[crazydago]

  I would double check the Gap of the plugs again. They are to be .031 to .035 , if to small a gap or to large , will make a problem noticed after you put some miles on them. GOOD LUCK WITH THE PROBLEM.

[Sodbuster]

+1 on the vacuum hoses. Check the hoses coming from the carbs to see if they have a hole in them.
When I bought my bike the carb vacuum hoses had holes in them and had to replace them. That alone eliminated most of the popping but ended up turning the pilot screws out to 2 1/4 turns and that took care of any popping there was.

[texaninsouthfl]

Thanks to all for the suggestions... seems like the consensus is to look for vacuum leaks and check o-rings. I'd already planned to buy the de-smog kit and do that when I take off the tank to check for leaks. Maybe I'll get the vacuum hose kit and o-rings from Redeye while I'm at it.

It'll be nice to get rid of this infernal noise... it's diminishing (a little) the pleasure I get from riding.

[texaninsouthfl]

Woo hoo... my Fat Lady doesn't snap, crackle or pop anymore! 

"The Beast" was desmogified today... found that the two vacuum lines to both middle carbs had big cracks in them... changed all the o-rings while we were at it and set the pilot screws to 2 and a quarter out like everyone seems to recommend. (they were apparently set 2 and THREE quarters out by the PO). Also found out that a K&N had already been installed so will be either selling or sending back the one I had bought.

It took my mechanic and I (he's the smart one) about 5 hours total to get it done but it was well worth it. It was good to have two pairs of hands to get the cursed airbox back in.

Besides eliminating the infernal backfiring and popping, she idles better and the exhaust note sounds a little different... hard to describe exactly... but "cleaner" sounding somehow. The top end seems to have improved too... not sure if that is from eliminating the vacuum leaks or changing the setting on the pilot screws.

Props to Redeye... excellent "shiny desmog kit" and pilot screw tool. All the parts fit perfectly and his instructions were spot on.

Took a 100 mile round trip ride down to Bikes & Beauties event at Cafe 27 ... ran like a beast!

And that's a wrap... 

[Sodbuster]

Sounds like someone is one happy camper 

[salty1]

Hey that's great she's herself again! However, I would do one more thing and that is synchronize the carbs. That is the frosting on your cake! 

[Hedgehog]

Interestingly, having just restored the piggies, there's much less popping.

I used to get flames out of the back under hard decel, with a loud pop sound. I never worried about it.

HH

[FryeVRCCDS0067]

The worst poping/backfiring I've had was the result of bad gas I got in North Dakota. If you always buy your gas from the same place, try a different brand. The other problem I've had which almost caused to me pull my carbs was bad vacuum caps on the intakes. If you wrap your hand around the intake runners you will feel nipples on the back of them. On my bike all have vacuum caps. The caps on the kickstand side seem to go first, probably because of gas condensing in them when parked.

They may look fine but run you finger back and forth over the end of the cap. If it's shot you will see and feel the cap open where it's dry rotted.

Also, did you tighten your plugs with a torque wrench? If they've loosed up they will overheat since they can't transfer their heat to the heads. One final thing, you might have just gotten a batch of bad plugs.